(guide-field-driven-design)=
# Field-driven design

A **field** is a value that changes from point to point: a stiffness, a color, a wall thickness. In OpenVCAD fields are attributes, so the same field can grade a part's material or drive a geometric size. These guides cover how to grade material, where field values can come from, and what happens when fields overlap.

| Guide | Focus |
| --- | --- |
| [Functional grading](gradients.md) | Linear, nonlinear, periodic, and distance-based gradients of scalars, colors, and volume fractions |
| [Fields: driving material and geometry](fields.md) | Build one field and use it for both material grading and geometric sizes |
| [Math expressions](math-expressions.md) | The expression syntax used by attributes and other nodes that accept spatial formulas |
| [Python functions for attributes](numba-attributes.md) | Write attributes as small compiled Python functions instead of expression strings |
| [Attribute conflict resolution](attribute-conflicts.md) | Decide which value wins where parts with different attributes overlap |
| [Working with volumes](volumes.md) | Load sampled volumetric data, such as medical images, as a field on ordinary geometry |
| [Simulation-driven design](simulation-driven-design.md) | Bring a finite-element result back into OpenVCAD and grade material from it |

Start with Functional grading. The other guides can be read in any order.

```{toctree}
:maxdepth: 1
:caption: Field-driven design guides

gradients
fields
math-expressions
numba-attributes
attribute-conflicts
volumes
simulation-driven-design
```